1. Field of the Invention
This invention relates generally to home and business security alarm systems for securing outdoor appliances, and in particular to a security alarm system component for securing HVAC units.
2. Description of the Related Art
As the price of metal goes higher, theft of appliances with metal components increases. Some appliances, such as HVAC units, are typically located outdoors and generally unattended, which makes them easy targets for thieves.
There are many different options available on the market for securing unattended appliances. Most of them set off an alarm when a power cord or a coolant tube is sectioned. Some of these mechanisms use wires attached to the power cord or coolant tube. The wires form a closed circuit. When a wire is cut, causing the circuit open, the alarm is triggered. This type of systems is easy to compromise. The wires are generally affixed to the part of a power cord or coolant tube that is outside the appliance, and an experienced thief may cut a power cord or a coolant tube along the outer surface of an appliance without touching the wires.
Other systems for securing HVAC units detect fluid pressure inside the coolant tubes. When a coolant tube is sectioned, the fluid pressure drops and sets off the alarm. This kind of systems is relatively harder to compromise. But they require replacing or cutting open the coolant tube for installing pressure sensors if the alarm system is not installed at the same time with the HVAC unit. The installation cannot be done by lay persons because not only it may be too dangerous or complex but also tampering with an appliance may void the warranty.
Some systems set off an alarm when the copper inside the appliance is removed. See. e.g., U.S. Patent Application Publication No. US2003/0201892 A1 (the “Chance” application). In Chance, tethers are soldered to copper components inside an HVAC unit and connected to pressure switches. The pressure switches normally maintain the alarm system circuit in a closed position. When a component is taken out of the HVAC unit, the tether attached to the component is pulled against the pressure switch which then opens the alarm system circuit and triggers the alarm. Again, installation of such systems is not a task for lay persons.
What is needed is a security alarm system for securing outdoor appliances that is both effective and easy to install. It is also desirable that such a system is inexpensive.